Topical administration of certain prostaglandins (PGs) has been known for more than twenty years to reduce intraocular pressure in several non-human species. However, their clinical use has been limited by early experimental observations of blood-aqueous barrier disruption with concomitant anterior chamber cells and flare. During the past several years, PG analogs have been developed which retain the ocular hypotensive effect but have minimal, if any, influence on the blood-aqueous barrier in human patients. These agents are now known to reduce intraocular pressure by increasing uveoscleral outflow. Although the biologic basis for the increased facility is unknown, altered turnover of ciliary muscle extracellular matrix linked with G-protein activation may be involved. The proposed studies will continue our investigations of eicosanoid actions on the outflow pathways through an analysis of PG modulation of extracellular matrix metabolism in human ciliary smooth muscle cells. PG-mediated effects on ciliary muscle cell production of extracellular matrix molecules including collagen types I, III, IV, fibronectin, and laminin will be determined. Changes in mRNA coding for these molecules or their subunits also will be determined. Ciliary muscle from monkey eyes treated in vivo with topical PGs will be analyzed for the alterations in the specific content of extracellular matrix molecules, matrix-degrading enzymes, regulatory molecules (TIMPs) and messages for these molecules or their subunits. In parallel experiments, PG-treated eyes will be sectioned and processed to determine the distribution of these molecules and their corresponding messages by immunocytochemistry and in situ hybridization. The role of G-proteins in mediating the responses of ciliary muscle cells to PGs will be investigated using agonist induction of GTP-gamma-S hydrolysis in ciliary muscle membranes The identity of specific G-protein alpha subunits activated by PGs in ciliary smooth muscle will be determined using a covalently-binding GTP analogue. These studies will provide new information about extracellular matrix biology in the ciliary muscle and will enhance our understanding of PG ocular hypotensive action.